1. Technical Field
The technical field relates to a focus adjusting apparatus for automatically adjusting a focus, and more particularly to a focus adjusting apparatus having a function for correcting backlash of a lens driver. Further, the technical field relates to an imaging apparatus mounted with such a focus adjusting apparatus.
2. Related Art
In general, it is known that a lens driver for driving a focus lens and the like has backlash in digital cameras. The backlash causes an error at the time of driving a lens to a target position in a focusing operation. For this reason, the backlash should be taken into consideration to make accurate control, and various techniques that cope with the backlash are developed (for example, see JP04-042674A and JP05-060968A).
For example, before a movement of the lens for focusing on a subject is started, backlash should be corrected. For this reason, before normal driving of the lens, it may be considered to move the lens by a moving amount corresponding to the backlash with a lens driver. However, when the lens is moved in order to eliminate the backlash, a contact sound of the lens and the lens driver or a driving sound of the lens driver during the driving of the lens may occasionally occur. In recent years, a digital camera that can capture not only a still image but also a moving image has made an appearance (for example, see JP2008-42404A). When such sounds are loud at the time when such a digital camera captures a moving image, the sounds are disadvantageously recorded as noises.
Further, for a contrast detection-type autofocus (AF) operation for determining a focus position based on an evaluation value of an image captured by an imaging device such as a CMOS sensor, an accurate focus lens position is important. However, when backlash occurs, an accurate focus lens position cannot be obtained, so that a malfunction disadvantageously occurs in the focusing operation.